Water-soluble coating composition for paper



Patented Sept. 21, 1948 2,449,812

UNITED STATES PATENT OFFICE WATER-SOLUBLE COATING COMPOSITION FOR PAPER Laurence R. B. Hervey, Concord, and Alvin C. Whitaker, Boston, Mass., assignors to the United States of America as represented by the Secretary of War No Drawing. Application August 27, 1945, Serial No. 613,012

1 1 Claim. (Cl. 260-295) This invention relates to disposable writing writing surface and to opacify the sheet, thereby surfaces, and more particularly is directed to a enhancing the receptivity to writing. it is depaper base coated with a water-soluble substance sirable to add an .opaciiying pigment to the coatcapable of being written upon with ink and ing composition. In instances wherein it is conpencil. 5 templated that the coated paper is to be de- It is an object of this invention to provide a stroyed by mastication and swallowing, it is addisposabie paper having a water-soluble coating I visable to incorporate a, small quantity of flavorwhich may be legibly written upon with ink'and ing or sweetening material in the coating compencil. position to render it more palatable. The spe-- It is another object of this invention to provide .10 ciflc materials used and the relative proportions a disposable paper having a water-soluble coatthereof may be varied according to the propering which is stable under extreme climatic conties desired in the final product. ditions and does not exhibit any tendency to be- The desired final product for-military security come brittle or tacky under such conditions. use should be a paper having a writing surface A further object of this invention is to provide coating that will take either ink or pencil writing a material having a writing surface that is stable with complete legibility. It should also be capaunder adverse climatic conditions and quickly ble of withstanding tropical, Jungle, arctic, and disposable upon being brought into contact with desert climatic conditions without breaking, water. cracking, or sticking together when folded,

The foregoing and other objects and advanpressed, or creased: and, it must be disposable by tages of the invention will ,be more apparent wetting with water in the aforementioned oilfrom reading the detailed description in the folmates, or upon mastication, and it should be lowing specification. possible to chew and swallow a small sized piece The invention comprises, generally, coating a of the coated paper without any injurious backing sheet with a water-soluble coating comeflects.

position that is receptive to ink and pencil writ- A product having the above desired properties ing which will remain legible under adverse 011- is obtainable by coating the preferred paper of matic conditions. I six and a half pounds weight per ream with a Any light paper backing sheetis suitable for composition comprising: the coating composition, described hereinafter. I Parts by weight The preferred backing sheet, however, is paper Polyvinyl alcohol 75 employed in mimeograph stencil backing. If the Ethyl alcohol solvent 300 coated paper is to be such that it may be per-' Water 30o sonally destroyed by mastication and swallow- Titanium dioxide pigment 90 ing, it should be of vegetable fibre composition SorbitOl Lactate 64 and have a weight approximately six and a To this composition 0.25 part by weight of sachalf Pmmds Per ream of five hundred sheets charin, USP insoluble, may be added to impart measuring tWO by three feet. a b n t t product V v This relatively light weight vegetable fibre pa- Various grades f the ingredients employed 1 P is mated a P' Water-Soluble 40 the composition are available all of which are composition t t W111 c ink and Pencil Writ suitable in practicing this invention. The proing in & leglble condltlon in hot, 101d, dry and portions given above, however, may vary slightly moist environments- It has been found that a with the different grades to obtain the most depolyvinyl alcohol dispersed in a suitable solvent sirable final product In making th mating will provide a coating composition having the 5 composition, the polyvinyl alcohol is first en a properties d The Polyvinyl aloopersed in the ethyl alcohol solvent and then the hol selected should be soluble in cold or hot wawater is slowly added t congbant stirring to ter, however, since some Of the desirable polyprevent the poIyvlnyl alcohol from lumping, It vinyl alcohols are difiicultly soluble; it is advisable i advisable t warm t mixture slightly to to incorporate a softening and solu iliz n a n cilitate solution. The other ingredients, titasuch as an ester of a p y y ic h in the nium dioxide, sorbitol lactate and saccharin are composition to render it more soluble and easily added to the mixture, which is then passed disposable, care being taken that the quantity through a colloid mill, or other suitable device, of softening agent added does not render the to completely disperse the titanium dioxide composition tacky. In order to provide a better pigment.

The coating composition must be diluted to proper coating consistency before it can be applied to the paper base. A mixture of equal parts by weight of water and methyl alcohol solvent is an eflective and efficient diluent, and 826 parts by weight or this mixture will-dilute the coatin composition to an excellent coating consistency.

The coating composition diluted to a coating consistency is placed in a vat and the paper base floated thereon. 'The paper picks up approxi mately two and a half times its weight of coating solids and is then passed over a doctor roll and dried in a low temperature drying oven according to standard practices in the paper coating industry.

Several tests were conducted on the coated sheets to prove the utility under adverse climatic conditions. Each sheet was written upon with ink and pencil and some of the sheets were tested separately. others were stacked and placed under pressure, while the remaining sheets were folded and placed under pressure. 'These units, single sheets, stacked sheets under pressure, and folded sheets under pressure, were stiamitted to the following different environments and periods of exposures: a temperature of 100 F. and a relative humidity of 90 per cent, for twentyfour hours; a temperature of -20 F. for two hours; and, a temperature of 159 F. and a relative humidity of 20 per cent, for 6 hours. After 30 2,330,314 being subjected to the above environments the written material on the sheets was still legible.

The sheets, single, folded and stacked, were flexibie and could be rolled, folded and creased without sticking. cracking or breaking. These simulated tropical, arctic, and desert climates apparently had little or no efiect upon the coated paper Parts by weight Polyvinyl .acohol '75 Ethyl alcohol 300 Water 300 Titanium, dioxide 90 Sorbitol lactate 64 LAURENCE R. B. HERVEY. ALVIN C. WHITAKER. REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,256,853 Schwartz Sept. 23, 1941 Schwartz Sept. 28, 1943 2,333,624 Altman Nov. 9, 1943 2,350,964 Loder June 6, 1944 

